Pi 3B+ jack audio inputs and low latency

Question

I need to be able to input several jack microphones (minimum 2, more could prove useful) to my raspberry, to do some audio processing (between all inputs), and output to a speaker. To make things worse, I also require a low processing latency between microphones and speaker (2ms would be good, and ~6ms is too much).

I've found a list of possible expansion boards that would allow me to do this: https://elinux.org/index.php?title=RPi_Expansion_Boards#Sound Specifically the audio injector stereo sound card seems to have 2 inputs, and the audio injector octo sound card has more than enough. I can't find the documentation for any of these cards on how much latency they may have, however.

The other sound cards on the list seem to have only 1 audio input.

I'd like to know if there are any other expansion cards (for the PI 3B+) or the latency of the cards I mentioned.

Edit: some extra info from "Is Raspberry PI 2 B suitable for a real-time audio effects application?" mentions operating system has a big impact on this delay. If so- are there any OSes that are better for this purpose, or would it be better to do kernel coding as that thread suggests? (and is it accesible/easy to do so)

Edit: after some more research, a better option seems to be beaglebone with a "bela" extension on top, as it has a custom operating system that allows for the sound to be processed separately, thus reducing latency.

Please note that answers (though in this case that answer seems to be "not with the Pi...") should preferably be posted as answers not edited into the question. — Ghanima, Jun 10 '19 at 22:04
@Ghanima alright, I'll do that. Indeed, sadly it seems that the raspberry does not have a specialized audio shield for extremely low-latency programs! I wish it was not the case, as it would've been a lot cheaper :) — ZeroZ30o, Jun 10 '19 at 22:08

score 3 · Accepted Answer · answered Jun 10 '19 at 22:11

I can confirm, after having used the Bela shield on top of a Beaglebone Black, that its latency is extremely low (<1ms) and quite capable of doing calculations on audio.

The normal shield has 2 jack microphone inputs and 1 jack stereo output. Strictly speaking, you have to buy the version that comes with jack adapters, though.

I do believe more inputs/outputs can be had with the analog pins, but I don't require them. They do however, provide another cape that does just that.

Pi 3B+ jack audio inputs and low latency

1 Answers1